This invention relates to electrically programmable fuses, and particularly to an electrically programmable fuse including anisometric contacts and a fabrication method thereof.
Electrically programmable fuses have been employed in many advanced technologies within the semiconductor industry. These fuses are utilized for various integrated circuit applications such as an implementation of array redundancy, field programmable arrays, and in chip-ID, and analog trimming circuits. These fuses may be programmed to store data on an integrated circuit, to adjust components on the circuit or to program logic on the circuit, for example. In a typical electrically programmable fuse the contacts are symmetrically positioned for easier printing and optimization of contact processing. The term symmetric refers to the number of contacts and the shape of the contacts being primarily squares (i.e., symmetric). Conventional fuses also typically have a large landing region for the contacts, several times the actual fuse link width.
There are several problems associated with the contacts in the conventional fuses. For example, during electromigration, when a programming current is applied, instead of heat generation being confined to the middle of the fuse link, the contacts can also raise in temperature thereby causing degradation of the contact which may cause the fuse to fail to remain in the programmed state. If a large symmetric contact is used, while solving the contact degradation issue, the thermal mass of the system increases, thereby requiring very large programming current. The large contact landing region of the conventional fuse also contributes thermal mass, requiring high programming current and increasing the risk of contact degradation.